While IDC doesn't typically break out Windows vs. Chromebook sales, IDC analyst Linn Huang confirmed the milestone to The Verge. "Chrome OS overtook Mac OS in the US in terms of shipments for the first time in 1Q16,"

While the IDC did not offer any specifics on Chromebook shipment numbers, it did state that 1.76 million Macs had been shipped to the U.S. in the last quarter, which means the Chromebook numbers have to be above that, perhaps as high as 2 million. Huang added that Chromebook in the U.S. are still mostly going to the K-12 education market, which has been the case for the last few years.

Google has been trying to get more businesses and consumers to buy Chromebooks. Later today, the company is supposed to reveal details on how it plans to bring the massive amount of Android apps, and the Google Play Store, to Chromebooks as part of its I/O 2016 developers conference. That could make Chromebooks more attractive to a larger audience.